iPad mini recognizing epub files as audiobooks

When I open iBooks on my MacBook Pro (OS X Yosemite 10.10.5) I can view/read all of my epub books (over 500+). However, when I sync my new iPad mini 2 (8.4.1) they're synced as Audiobooks (only around 79 or so are actually recognized as ebooks). iTunes also recognizes them as audiobooks - but they're in fact epub files. On my older iPad (I believe it's a second generation that had the same OS) I never had this problem. What can I do to fix it? As of now, my entire iBooks library is useless on my iPad mini 2 - reading on this device was my primary reason for buying it 😟